This invention relates to a system, comprising apparatus and method, for the performance of various activities in space, such as servicing, repair and maintenance of satellites, space craft, space transportation systems, space stations, and the like. More particularly, the invention relates to a system for the remotely controlled performance of unmanned extravehicular activity in space, as by example from the interior of an orbiting shuttle vehicle.
From time to time, equipment placed in space around the earth, such as communications satellites and the like, develop malfunctions. In many instances, the nature of the malfunction is known or can be ascertained and could be readily repaired if access to the equipment could be had. The most notable example of this was the Solar Maximum (Solar Max) satellite malfunction due to the failure of an electronic panel in the interior of the satellite. The malfunction was repaired by the replacement of the defective electronic panel in the course of the widely publicized Solar Maximum repair mission. However, the repair was delayed for more than two years, first by a year of development of a payload integration plan for the mission involving the development of hardware, scenarios, transition paths, worksites, tools, extravehicular activity techniques and associated operational support, and the like, followed by a year of training of the astronauts selected to perform the extravehicular repair activity. As part of the same mission, the attitude control system mounted on the exterior of the satellite was replaced and a baffle was placed over the exterior vent of the satellite's X-ray Polychromator unit.
To carry out the Solar Max repair mission, the STS-41C space shuttle, equipped with a remote manipulator system, was launched into orbit and maneuvered to rendezvous with Solar Max. With the shuttle parked near Solar Max, one astronaut using a manned maneuvering unit flew to the satellite and stopped its rotation. The satellite was grappled by the end of the shuttle's remote manipulator arm and brought by the arm to a berthing ring in the shuttle's cargo bay. The repair activities were carried out by two crewmen working outside of the shuttle, one from a work station having hand holds and foot restraints to hold the astronaut in place and located at the end of the remote manipulator arm, and the other moving freely about the cargo bay. The tools and equipment necessary for the repair tasks were stored in a tool locker in the cargo bay and the replacement parts were stored in a storage area and fixed in place.
To remove the electronics box, which is about the size of a brief case, and install a new one, the astronaut had to open a panel in the satellite's shell at the location of the box. He had to cut through the foil insulation and remove screws that secured a protective thermal blanket over the box. After taping the thermal blanket and insulation out of the way, he then had to install a hinge to convert the panel that covers the main electronics box into a door. The remaining screws retaining the panel were then removed and the panel opened, supported by the hinge. Cables from the electronics box were unplugged, the box was removed and passed to the other astronaut who then handed the replacement electronics box to his partner. The new box was installed, all connections were remated, the door was closed and secured, and the protective insulation was reattached. Thereafter, Solar Max was grappled by the manipulator arm and moved outside of the cargo bay for redeployment in orbit. The above procedure is described in greater detail in National Aeronautics and Space Administration Publication EP-205 entitled "Repairing Solar Max."
The Solar Max repair as described required the services of three astronauts, two of whom participated in the extra-vehicular activity while the third remained inside the shuttle cabin. Apart from the two year delay in making the Solar Max repair, all of the astronauts were subjected to the hazards of space flight and those participating in extra-vehicular activity were subjected to the additional hazards which that entails. It is the principal object of the present invention to provide a system by which servicing, repair and maintenance functions similar to the Solar Max repair may be carried out using a remotely operated bilateral force reflecting telerobotic system and remotely changeable tools operated from a gravity-free space craft cabin environment by a single crew member.